Conventionally, Patent Document 1 discloses a vehicular air conditioning device that heats a vehicle compartment by heat dissipated from a heater core. The heater core heats the vehicle compartment by using a coolant heated by heat dissipated from an engine.
In this conventional technology, the coolant can be heated by a water-refrigerant heat exchanger as well as the engine. The water-refrigerant heat exchanger is a heat exchanger that heats the cooling water of the engine by using a refrigeration cycle.
According to this, the cooling water can be heated by heat dissipated from the water-refrigerant heat exchanger to heat the vehicle compartment even when the heat dissipation amount of the engine is small.